Higher-Order Estimations of Load Factor from Derived Gust Velocity

Abstract

Pratt’s formula, in which the aircraft is modeled as a single-degree-of-freedom system, is used extensively to extract derived gust velocities from measured normal acceleration. There is evidence that airframe mass distribution along the longitudinal axis can affect the gust load alleviation factor. In this paper, the inclusion of the pitching degree of freedom in the model is explored, accounting for the aircraft mass distribution along the longitudinal axis. Two different two-degree-of-freedom models are presented and numerical solutions are offered. A typical heavy transport aircraft is used for illustration. It is shown that the inclusion of the second degree of freedom results in as much as 10% reduction in the magnitude of the gust load alleviation factor.